Continuous fluid-solid contact process

ABSTRACT

THIS INVENTION RELATES GENERALLY TO FLUID-SOLID CONTACT PROCESSING SYSTEMS, AND, MORE PARTICULARLY, TO SUCH SYSTEMS AS MAY BE USEFUL IN ION EXCHANGE PROCESSES, WHICH PROCESSES OPERATE IN A TRULY CONTINUOUS MANNER AND EMPLOY CONTINUOUSLY MOVING POROUS BEDS FOR PROVIDING THE FLUID-SOLID REACTION, REGENERATION, AND WASHING OPERATIONS, AS DESIRED, AND WHICH UTILIZE UNIQUE MEANS FOR ISOLATING THE FLUID FLOW BETWEEN OPERATION ZONES THEREOF TO PROVIDE HIGH FLOW RATES FOR THE PROCESSED OUTPUT PRODUCTS INVOLVED.

Aug. 7, 1973 so ET AL 3,751,362

CONTINUOUS FLUID-SOLID CONTACT PROCESS Filed July 8, 1971 4 Sheets-Sheet1 102 lol m I07 I08 }ll6 '00 103 INVENTORS AIN A.SON|N RONALD F.PROBSTEIN @EF SHWARTZ Fle r BY 57 M" T T'Ys Aug. 7, 1973 A, SONIN ET AL3,751,362

CONTINUOUS FLUID-SOLID CONTACT PROCESS Filed July 8, 1971 4 Sheets-Sheet2 UNTREATED I9 I 3| 2 PRESSURE.

LIQUID PRIMARY REACTION zoNE II 38 2| 2o TREATED LIQUID e OUTPUT PRODUCTPOROUS II BED I8 37 38 WASHING DILUT ED 5 39 AND REGENERANT REGENERANTSEPARATION LIQUID REGENERANT ZONE 4I Q INPUT PUMP \P4 27 28 35REGENERATION WASTE 36 ZONE I2 3 OUTPUT A 26 40E SEPARATION 25 ZONE 42RESIN DRIVER l4 zoNE I3 FIGS 33 I ATMOSPHERIC I FIGSA Aug. 7, 1973 A. A.SONIN ET AL 3,751,362

CONTINUOUS FLUID SOLID CONTACT PROCESS Filed July 8, 1971 4 Sheets-Sheet4 UNTREATED .I l L I I I I INPUT /|7 -Q 32 i, FEED PUMP PRIMARY REACTIONM J SS ZONE l| TREATED J L LIQUID OUTPUT 2O PRODUCT RESIN 25 26 DRIVER38 ZONE l3 37 p 39 To FEED PUMP I7 40 36 D WASTE REGEN. OUTPU REGENERANTPUMP LIQUID as INPUT REGE NERATION ZONE I2 United States Patent3,751,362 CONTINUOUS FLUID-SOLID CONTACT PROCESS Ain A. Sonin, Boston,and Ronald E. Probstein, Brookline, Mass, and Josef Shwartz, Haifa,Israel, assiguors to Avco Corporation, Cincinnati, Ohio Filed July 8,1971, Ser. No. 160,601 Int. Cl. 301d 15/02 US. Cl. 210-33 17 ClaimsABSTRACT OF THE DESCLOSURE This invention relates generally tofluid-solid contact processing systems, and, more particularly, to suchsystems as may be useful in ion exchange processes, which processesoperate in a truly continuous manner and employ continuously movingporous beds for providing the fluid-solid reaction, regeneration, andwashing operations, as desired, and which utilize unique means forisolating the fluid flow between operation zones thereof to provide highflow rates for the processed output products involved.

DESCRIPTION OF THE PRIOR ART Many fluid-solid contact systems have beenused or suggested for use in the prior art and, from the viewpoint ofoperating continuity, such systems generally can be said to fall intothree main categories: a first category sometimes identified as batch ordiscontinuous processing systems; a second category which can be mostaccurately identified as semi-continuous or nearly continuous processingsystems (although, in some cases, such systems have been inaccuratelyreferred to as continuous even though intermittent operation occurstherein); and a third category which accurately can be referred to astruly continuous processing systems.

A useful summary of the historical development of such fluid-solidcontact processing systems, particularly of the latter two types asapplied to processes involving ion exchange principles, is given in thepublication Systematic Analyses of Continuous and Semi-Continuous IonExchange Techniques and the Development of a Continuous System, by R. C.Clayton, presented at the Society of the Chemical Industry Conference onIon Exchange in the Process Industries, July 16-18, 1969, theproceedings of which were published by the Society in London, England in1970. This paper traces primarily the development of nearly continuousand continuous ion exchange systems from the middle 1950s when recentinterest in providing improved systems utilizing improved resins wasbegun.

Perhaps the most Widely known nearly continuous systems currentlyproposed and available for use are those developed by I. R. Higgins,examples of which are described in US. Pat. No. 2,815,322 issued to I.R. Higgins on Dec. 3, 1957, and in the publications, Chem- SepsContinuous Ion Exchange Contactor and Its Applications toDe-mineralization Processes, by I. R. Higgins and R. C. Chopra,published as part of the above referenced conference, and Continuous IonExchange of Process Water, by I. R. Higgins, published in ChemicalEngineering Progress, vol. 65, No. 6, in June 1969, as well as thosedeveloped by the Asahi Kasei Koygo Kabushiki Kaisha Corporation ofJapan, various embodiments of which are described, for example, in US.Pat. No. 3,152,- 072 and British Pat. Nos. 1,022,921; 1,023,943;1,036,065; 1,036,560; 1,036,559; 1,036,429; 1,033,649 and 1,031,299 aswell as a recent publication Development of the Degremont-AsahiContinuous Ion Exchange Process, by I. Bouchard, also included as partof the above-referenced conference.

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Both the Higgins and the Asahi systems, as described in the patents andpublications listed above, provide what are best referred to as nearlycontinuous systems, the operations thereof not being truly continuous,the latter term as used herein meaning all elements of the system remainin continuous operation without any interruption during the overallreaction, regeneration, and rinsing steps of the process. Both theHiggins and the Asahi systems are appropriately programmed so thatprocessing is interrupted at some point during the overall operation fora finite time period. Such operation has been referred to as one usingan intermittently moved, fixed bed process and is further discussed inthe publication, Development of a Continuous Ion-Exchange Process, by D.G. Stephenson, also published in the proceedings of the abovementionedconference.

Moreover, in the operation of such systems, separate columns or regionsseparated by valves are utilized for the ion exchange portion of theoverall process, the regeneration portion thereof and the rinsing orwashing portion thereof. The exchange step effectively takes place withthe use of a fixed bed of ion exchange resin which is intermittentlymoved so that the depleted resin can be conveyed from the ion exchangecolumn to the regeneration column and regenerated resin can be insertedinto the ion exchange column during the period of intermittent bedmovement. During such periods the supply of untreated liquid is shut offso that no such liquid enters the ion exchange column until the depletedand regenerated resins are appropriately moved into position.

Moreover, in both the Higgins and the Asahi systems the depleted orregenerated resin materials which are moved from one station within thesystem to another are conveyed through a plurality of valves, or othermechanical devices, the use of which tends to cause a deterioration ofthe resin material and, hence, an attrition thereof.

Examples of truly continuous processing systems are briefly discussed inthe above-mentioned paper of Clayton and are more completely describedin the articles Countercurrent Ion Exchange, by T. A. Arehart et al. inChemical Engineering Progress, vol. 52, No. 9, September 1956, p. 353;Semicontinuous Countercurrent Apparatus for Contacting Granular Solidsand Solution, by C. W. Hancher and S. H. Jury, Chemical EngineeringProgress Symposium Series, vol. 55, No. 24, 1959, pp. 96-97; andExchange Rates Going Up, in Chemical & Engineering News, Oct. 22, 1956,p. 5200.

Such systems suffer from several defects which have prevented them frombeing accepted for use by those in the art. In the system described inthe Chemical & Engineering News article, for example, the resinparticles move downwardly with gravity through the upwardly flowingliquid and tend to become fluidized if the liquid flow upwardly throughthe resin becomes too high. Such tendency can be overcome as shown inthe system described in the Arehart et al. article by the use of ahydraulic ram which tends to compress the resin and to maintain the bedin a packed porous state, the bed in turn being allowed to movedownwardly by the use of a jet device at the end of the column. Themajor disadvantage of these systems, as pointed out in the abovementioned Clayton article, lies in the extreme difliculty of maintainingthe delicate balance of pressures required at several points along theion exchange column in order to isolate the fluid flow in adjacent zonesthereof. Isolation is achieved in such systems by creating intermediatere gions containing virtually stagnant liquid, across which the pressuredifference is maintained at zero. At higher flow rates, pressureimbalances tend to occur, producing unstable operation of the entiresystem, and producing an undesirable mixing of the fluids in adjacentzones so that the desired isolation is not achieved. The critically ofsuch pressure balances can be alleviated to some extent, if the flowrates involved are reduced to a low enough value. However, theelimination of such instabilities can only be assured at flow rateswhich are lower than those required for a practically operating systemcompetitive with discontinuous or nearly continuous systems.

Thus, in the above described types of truly continuous systems of theprior art, the maximum flow rates of output product that can be achievedwith stable operation are only up to about 100 gallons per hour persquare foot of column area, as set forth in the Chemical & EngineeringNews article. Such output product flow rates are far lower than thoseachievable with the system for carrying out the process of ourinvention, as discussed more fully below.

STATEMENT OF THE INVENTION The method of this invention overcomes thedefects of prior art systems discussed above and provides a trulycontinuous system which operates at sufficiently high flow rates toprovide a high product output which is at least one order, and in somecases two orders, of magnitude higher than those provided by continuousor semicontinuous systems presently available or suggested for use Bythe art at comparable installation and operating costs.

The high output product flow rates are obtainable in the system forcarrying out the process of the invention by the use of an improvedmethod for providing isolation between fluid flows of adjacent operatingzones of the system. For clarity, the basic structural components andoperation thereof as used to so isolate the fluid flow therein provide aseparation region or zone in which, as described in more detail below,fluid flows can be continuously maintained during operation so that thestagnant or zero-flow region of prior art continuously operating systemsis not needed. The use of such unique isolation zones permits theoperation of the system at flow rates which,

provide output product flows of, for example, about 7000 gallons perhour per square foot of column area as opposed to the output productflow rates of less than 100 gallons per hour per square foot in theprior art. Unlike the prior art systems, the output product flow ratesin the system for carrying out the process of the invention are limitedonly by the maximum allowable compressive stress on the solid material(e.g., the resin beads) and not by any fundamental limitations orproblems inherent in the flow system.

Although not limited thereto, the invention can be specificallyprwticed, for example, in a single column appartus for providing a trulycontinuous ion exchange operation, either of a cation or anion nature. Aplurality of solid particles, such as an ion exchange resin material,are formed as a packed porous bed in a non-fluidized state, that is, aporous bed in which the solid particles do not move within the beditself. The porous bed of solid resin material is initially formed froma slurry of such resin material in a non-regenerated form in a driverzone of a column, the method of formation thereof being substantiallythat described in US. patent application Ser. No. 748,811, filed on July30, 1968, by R. F. Probstein and J. Shwartz, now Pat. No. 3,587,859. Theporous bed is caused to move through the regeneration and primaryreaction zones of the column and independent control of the rate of suchmovement is provided by a control of either the resin removal rate inthe column or of the restraining forces, together with an appropriatechoice of the pressure differences between the various inlet and outletports. The porous bed of resin material is removed from the columnfollowing its contact with the fluid in the primary reaction zone of thecolumn and is combined with a portion of the untreated fluid and theslurry is thereupon conveyed to the initial driver zone for reformationof the porous bed therein. In the system for carrying out the process ofthe invention it is not necessary to convey the solid material throughan excessive number of mechanical devices, such as valves, pumps, orother devices, and, in one preferred embodiment thereof, the system isarranged so that such material passes only through a single slurry pump,thereby minimizing the resin attrition, and a scraper which acts as arestraining force and control at the top of the column. The scraper maybe designed to have relatively little physical effect on the solidparticles.

Further, the fluid flows in the primary reaction zone and in theregeneration zone are isolated from each other and the fluid flows inthe regeneration zone and in the driver zone are also isolated from eachother. The isolation is achieved by the formation of isolation zoneswhich are maintained in a stable condition through the use of fluiddisplacement techniques so that instability of operation cannot occureven under conditions of high flow rates as discussed more fully below.

Once the system for carrying out the process of the invention has beenset into motion no programmed operation thereof, particularly one whichprovides for some intermittent or non-continuous operation, is necessaryand the system continues its operation without interruption and merelyrequires appropriate monitoring means to determine that no unwarrantedor accidential operating problems have arisen. Alternatively, it iswithin the scope of the invention that the system for carrying out theprocess of the invention may be programmed for a specific purposedesired in a particular use of the invention. For example, it may bedesired that the rates of product removal required may be different overdifierent time periods and the operation of the system may be purposelyprogrammed to provide such varied rates.

Because of the presence of stable isolation zones, the ion exchangeoperations which occur in the process, whether in the primary reactionzone or in the resin regeneration zone, can be substantially localizedso as to remain in elfectively stationary positions within the column,and, because all of the zones that are used can be of substantiallylimited lengths, the overall inventory of solid material for the processis reduced considerably from that which has been necessary in previouslyused processes of the prior art.

The system for carrying out the process of the invention provides animproved efiiciency of operation over that obtainable by systems of theprior art both with regard to the primary ion exchange reaction processand the resin regeneration ion exchange process because of the systemstruly continuous operation. Further, such efiiciency is obtained atlower costs than those required with presently known systems since in apreferred embodiment only a single column providing greater output flowrates per unit of column volume need be used, less solid resin materialrequired to produce the same output production rate using the samematerials need be used, less regenerant material need be used, and amuch less complex control system need be used, all as compared to knownprior art systems.

DESCRIPTION OF THE DRAWINGS A more detailed description of the inventionas used, for example, for ion exchange processes, is described belowwith reference to the following drawings wherein:

FIGS. l, 1A, 2, 3 and 4 show various embodiments of the basic isolationzone configurations used in connection with the invention;

FIG. 5 shows in diagrammatic form one preferred embodiment of an overalloperating column representing the system of the invention;

FIG. 5A shows a graph of the pressure distribution along the columnshown in FIG. 5;

FIG. 6 shows an alternate columnar embodiment of the system of theinvention;

FIG. 6A shows a graph of the pressure distribution along the columnshown in FIG. 6; and

FIG. 7 shows a portion of another alternate embodiment of the invention.

FIGS. 1, 1A, 2, 3 and 4 show various forms of a basic operatingcomponent used in particular embodiments of the invention for providingeflective isolation of the fluid flows present in adjacent operatingzones of the system.

As shown in FIGS. 1, and 2, isolation can be provided between the flowsof fluids outwardly from adjacent zones of a column filled with acontinuously moving porous bed of solid material in which bed the fluidsin such zones flow in opposite directions. In the first case (FIG. 1)both fluids are to be extracted from the column in pure, or unmixed,form. Thus, in a column 100 a first fluid 102 flows in one directionfrom a zone 101 as shown by the arrows associated therewith in thefigure, While a second fluid 104 flows in the opposite direction from azone 103 toward the first fluid, also as shown by the arrows associatedtherewith. A separation, or isolation, zone 105 is present intermediatezones 101 and 103 and small portions of fluid 102 and 104 flow in theisolation zone and together flow outwardly from a port 106 therein. Themajor portions of fluids 102 and 104 flow outwardly from the column atports 107 and 108 in their pure form respectively. It is assumed, forexample, that the porous bed is moving Within the column from zone 103to zone 101. A portion of the fluid 104 from zone 103 is carried intozone 105 with the solid particles of the bed and is displaced by aportion of the fluid 102 flowing into zone 105 from zone 101 in acountercurrent washing action and the displaced portion of fluid 104together with the displacing portion of fluid 102 flows out through port106. An isolation crown 109 is formed near port 106 and none of fluid104 is permitted to flow beyond crown 109 into zone 101, while at thesame time none of fluid 102 is permitted to flow in the other directionbeyond crown 109 into zone 103.

The portions of fluids 102 and 104 which exit at port 106 can be keptvery small by an appropriate choice of pressures at ports 106, 107 and108 providing the desired pressure differentials along the columnbetween such ports as discussed more fully below in connection withFIGS. 5, 5A, 6 and 6A. Thus, while small portions of the fluids are ineflect lost due to their flow outwardly at port 106, any loss thereofcan be kept very small and the advantage gained in maintaining a stableisolation zone far o'tfsets any disadvantage in such losses, because thefluid flow rates in the system can be increased markedly so that theproduct output rate is at a relatively high value in comparison to priorart values. Thus, in an operating column using the techniques of theinvention, the output product flow rate can be improved by one or moreorders of magnitude in comparison with the product output rate incontinuous columns of the prior art using stagnant zone separation withits inherent instabilities at other than minimal flow rates.

FIG. 1A shows a similar situation in which fluid flows in adjacent zonesare in opposite directions. In this case both fluids are to be insertedinto the column and must flow therein in pure, or unmixed, form.Accordingly, fluid 112 in zone 111 is fed into a column 110 through port113 to move in the direction of movement of a porous bed assumed to bemoving from zone 116 to zone 111. A fluid 115 in zone 115 is fed intothe column through port 117 to move in a counterdirection to themovement of the bed. Small portions of each fluid move toward each otherin isolation zone 118 located intermediate zones 111 and 115 and suchportions exit together at port 119. In the same manner discussed above,the pressures at ports 113, 117 and 119 are arranged to provide pressurediflerentials appropriate for forming an isolation crown 120 near port119 and for controlling the portions of each fluid which flows outwardlyfrom zone 118 so that none of fluid 112 can enter zone 116 and none offluid 115 can enter zone 111.

In FIG. 2, isolation is achieved between two zones in which fluids alsoare flowing in opposite directions. However, in this case, only one ofthe fluids need be extracted from the column in pure or undiluted form.Accordingly, a fluid 121 flows in zone 122 in a direction opposite to anassumed direction of movement of a porous bed within a column 123, whilea fluid 124 flows in zone 125 in the same direction as such bedmovement. Fluid 124 is to be extracted at port 126 in pure form andfluid 121 which is extracted from port 127 may be permitted to be mixedwith a small amount of fluid 124. The pressures at ports 126 and 127 arearranged to form isolation zone 129 so that the major portion of fluid124 exits at port 126 and a small portion of fluid 124 moves with thebed toward port 127. Such portion is displaced by a portion of fluid 121and an isolation crown 128 is formed near port 127 at Which port all ofthe fluid 121 exits together with such small portion of fluid 124 whichhas been displaced so that none of fluid 121 moves into zone 125 andnone of fluid 124 moves into zone 122.

FIGS. 3 and 4 show situations in which both fluids are moving in thesame direction in a column which also has a porous bed moving therein.In FIG. 3 it is desired that a first fluid which exits from one zone ofthe column be prevented from contaminating a second fluid which entersthe column into an adjacent zone. Thus, a fluid 130 exits from a zone131 of column 132 at port 133, while a fluid 134 enters the column intoa zone 135 at port 136, both fluids flowing in the same direction withinthe column as shown by the associated arrows. A small portion of fluid130 flows toward zone 135 and a small portion of fluid 134 flows towardzone 131 and both portions exit the column at port 137 from an isolationzone 138. The pressures at ports 133, 136 and 137 are arranged so thatan isolation crown 139 is formed near port 137 and none of fluid 130enters zone 135 and none of fluid 134 enters zone 131.

FIG. 4 shows a situation in which fluids in two adjacent zones flow inthe same direction, one exiting from the column and one entering thecolumn, and only the entering fluid is to be prevented fromcontamination by the exiting fluid. Thus, fluid 140 exits column 141from zone 142 at port 143 and fluid 144 enters the column into zone 145at port 146. The pressures at ports 143 and 146 are arranged to formisolation zone 143 adjacent zone 142, an isolation crown 147 beingformed near port 143 so that all of the fluid 140 exits at such porttogether with a small controlled portion of fluid 144. The major portionof fluid 144 flows in zone 145 and none of fluid 140 enters zone 145 andnone of fluid 144 enters zone 142.

The terms isolation zone, or separation zone, are used interchangeablyin the description of the invention and are intended to refer to aregion within a column, lying between two zones which are to beisolated, in which region controlled portions of both fluids flow andwhich region includes an isolation crown and a port through which suchcontrolled portions are permitted to exit together from the column.

Thus, as can be seen in FIGS. 1, 1A and 3, the isolation zones 105, 118and 138 are shown as including the parts of the column depicted. thereinwhich lie between ports 107 and 108 in FIG. 1, between ports 113 and 117in FIG. 1A and between ports 133 and 136 in FIG. 3. Accordingly,controlled portions of both fluids flow in isolatron zones 105, 118 and138 and are permitted to exit from the isolation zones together at ports106, 119 and 137, respectively.

In the configuration depicted in FIGS. 2 and 4, wherein the controlledportions of fluids 121 and 140 included all of such fluids which flow inzones 122 and 142, respectively, the isolation zones 129 and 148 areshown as effectively extending from ports 126 and 146, respectively, tolocations above ports 127 and 143, respectively, so as to includeisolation crowns 128 and 147, respectively. Accordingly, controlledportions of both fluids flow in the isolation zones 129 and 149 showntherein and such controlled portions are permitted to exit from theisolatron zones together at the ports 127 and 143, respectively. One ormore of the above configurations can be used 1n various embodiments ofoverall systems for carrying out the process of the invention asdiscussed further below. FIG. shows one preferred embodiment of such anoverall operating structure in accordance with the process of theinvention, which structure, for example, utilizes a single columnprocessing system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 5 there is shown aprocessing column 10 which can be used, for example, to remove calciumfrom a calcium carbonate solution, such as might be found with hardwater, through a cation exchange operation wherein a suitable ionexchange resin including free sodium ions (Na is utilized for exchangewith calcium ions (Ca+ in the solution to be treated. Such an ionexchange process is exemplary only and other ion exchange processes, orprocesses other than those utilizing ion exchange principles, can alsomake use of the column as described herein.

Three major operating zones are utilized in column 10 and are identifiedin FIG. 5 as including two principal ion exchange zones. The first, aprimary reaction zone 11 for producing the output product, and thesecond, a regeneration zone 12 for regenerating the resin material; anda third, a resin driver zone 13. A washing and separation zone 41intermediate zones 11 and 12 is also shown, although, as discussed inmore detail below, the washing operation is not always needed in allapplications of the invention. Further, a separation, or isolation, zone42 is utilized intermediate regeneration zone 12 and driver zone 13.

The column has within it a moving packed porous bed 13 of an ionexchange resin, which bed extends from a position in driver zone 13shown by dashed line 14 at the lower end of column 10 to a positionabove the primary reaction zone 11 near the top end of the column asshown by dashed line 15. The untreated fluid, in this case a calciumcarbonate solution, is fed from a supply 16 thereof through feed pump 17to an input port 19 shown at the top end of the column. Although notnecessarily limited thereto, in the particular embodiment discussed inFIG. 5, the column is cylindrical and the fluid input and output portsused therein intermediate the ends of the column may extend about theentire periphery of the column, as shown.

The untreated liquid entering port 19 is thereby partly directeddownwardly as shown by arrows 38 through the upper portion of porousresin bed 18 so that as the untreated liquid is contacted by the resinparticles in the bed, the (Caions of the former are exchanged with, orreplaced by, the free (Na+) ions of the latter, as is well known. At thelower end of primary reaction zone 11 the liquid has been fullyprocessed, i.e., the calcium ions have been substantially completelyremoved and replaced by the free sodium ions, and treated liquid productis thereupon removed from the column through port 20 via a throttlevalve 21.

During the ion exchange operation the porous bed 18 is continuouslymoving upwardly through the primary reaction zone 11 and the untreatedliquid is moving in a counter direction downwardly through the zone. Theresin particles which have moved in the porous bed 18 through theprimary reaction zone and which are thereby present in the upper sectionof the column above zone 11 have at that point been depleted of theirfree sodium (Na ions to a predetermined level, and, accordingly, must beregenerated before they can be used again for that purpose. Theparticles in their depleted or non-regenerated form are mixed with aportion of the untreated liquid which enters through port 19 and theslurry removed from the column through port 32 as a result of the pressure difference between inlet port 19 and port 32. The resin of theslurry is carried with the liquid through line 29 to a location belowthe column 10 where it is fed to a slurry pump 33 which moves the slurryinto the lower end of column 10 via a slurry input port 34 at the bottomthereof.

The resin particles which enter the column in the slurry subsequentlyare formed into a compact porous bed in driver zone 13, which bed isforced upward by the fluid flow in the driver zone. The untreated liquidportion of the slurry is permitted to exit from the column at port 25and is then fed via throttle valve 26 to the input line at feed pump 17where it is returned to the supply of untreated liquid from supply 16.

An isolation, or separation, zone 42 is present between regenerationzone 12 and resin driver zone 13 so that the depleted regenerant liquidfrom zone 12 is prevented from reaching and mixing with the untreatedfluid which exits via port 25 and is returned to the feed. In thisseparation operation the depleted regenerant liquid which has passeddownwardly through the moving porous bed in regeneration zone 12 is usedto displace any portions of the untreated liquid which are present inthe bed as it moves upwardly from zone 13 and the depleted regenerantliquid together with such untreated liquid portion both exit at port 36to be pumped as output waste products. Such operation is the typediscussed above with reference to FIG. 2, for example. Accordinglyisolation, or separation, zone 42 extends to a location above port 36and an isolation crown 40 is formed near port 36 so that theregeneration zone 12 is effectively separated from the driver zone 13and depleted regenerant liquid is prevented from moving downwardly intozone 13 from zone 12, while untreated liquid is prevented from movingupwardly from zone 13 into zone 12. The pressures along the column, asdiscussed below, are arranged so that only a small, and controlled,amount of untreated liquid need be lost through port 36 to achieve theseparation. Although some regeneration takes place in the upper regionof isolation zone 42, it is clear that most of the regeneration actionoccurs in the regeneration zone 12.

Since the resin particles in the slurry entering the bottom of thecolumn are partially or wholly depleted of their exchangeable ions, suchions must be replaced through a regeneration process, which operationoccurs in regeneration zone 12. The regeneration liquid which in theexample under discussion may be a concentrated sodium chloride (NaCl)solution is fed to the column from a supply 27 via regenerant pump 28through input port 35. The major portion of the regenerant solutionforced under a pressure difilerence downwardly through the upwardlymoving porous bed in a countercurrent operation and in the process ofmoving therethrough the free sodium (Na+) ions therewith replace thecalcium (Ca++) ions present in the depleted resin particles inregeneration zone 12. The depleted regenerant solution then exits fromthe column via port 36 where it can be dumped as waste output material.Although, as mentioned above, most of the regeneration action occurs inregeneration zone 12, a small amount of regeneration takes place in theupper region of separation zone 42 prior to the removal of depletedregenerant solution from the column.

The porous bed of regenerated resin particles which moves upwardly fromregeneration zone 12 also contains a small portion of regenerant liquid.If the regenerant liquid is not removed from the porous bed it will becarried upwardly with the bed and will mix with the treated liquidproduct and will exit together with the treated liquid at port 20. Whilein some cases it may not be detrimental to have the treated liquid mixedwith regenerant liquid, in many other cases it is undesirable to permitsuch mixing to occur. In the lattter instances any upwardly movingregenerant liquid must be removed before it reaches port 29. Suchremoval is accomplished in Washing and separation zone 41 in a manner asdiscussed above with reference to FIG. 3. Thus, a wash liquid, in theform of a small portion of the treated liquid product moving downwardlyfrom primary reaction zone 11, is caused to move in a counter-currentdirection through the upwardly moving porous bed in a washing portion ofzone 41, and accordingly, displaces the regenerant liquid which ispresent in the moving bed. An isolation crown 39, as discussed above, isformed as shown. The displaced regenerant liquid exits from the columnat port 37 and is fed back to the input of regenerant pump 28 viathrottle valve 38 where it is added to the regenerant fluid from supply27. If the treated liquid which acts as a washing solution and whichexits from port 37 is held to a minimum, the regenerant liquid whichalso exits therefrom is only slightly diluted therewith. The presence ofsuch a relatively small amount of treated liquid in the regenerantliquid, which is combined ultimately with the regenerant liquid fromsupply 27, will cause a controlled change in the characteristics of theregenerant liquid so that the liquid supplied to zone 12 for theregeneration process has the desired concentration.

As discussed previously, the presence of isolation crown 39 formed nearport 37 effectively separates the liquids in the regeneration zone 12and in the primary reaction zone 11 and no regenerant liquid is carriedupwardly beyond crown 39 to zone 11 and similarly no treated liquid iscarried downwardly below crown 39, the small amount of the treatedliquid which moves downwardly from zone 11 being forced to exit at port37. Thus, a porous bed comprising regenerated resin particles enters theprimary reaction zone Ill so that the ion exchange process iseffectively carried out therein.

FIG. A shows the distribution of pressure along the column. The basepressure is, for example, arbitrarily taken to be atmospheric pressure Pand in this case, exits at port 36 where the waste material is assumedto be dumped into the atmosphere. The pressure P at port 25 is heldslightly greater than the pressure P its value being set by throttlevalve 26. The maximum pressure in the column is at the lower endthereof, that is, at the input to the resin driver zone 13, and isidentified as pres sure P The pressure P at port 19 at the upper end ofthe column is lower than P, so that the overall pressure drop (P Psubstantially provides the driving force for moving the porous bedupwardly through the column against the restraining forces therein.These restraining forces would include the frictional forces which mayexist between the bed and the inner surface of the column and anyadditional restraining force which may be present, such as the forcewhich exists in the column shown due to the stress exerted by thescraper 31 at the top of the column. In addition, if the column isoriented in a vertical direction, the weight of the porous bed will alsocontribute to such forces.

This rate of upward advance of the porous bed is governed either by therate of removal of the resin by the scraper or by the balance of forceswhich exist on the porous bed as a whole.

The pressure P, is determined by the pressure generated by theregenerant pump 23 and is greater than the pressure P at port 37, thelatter being set by adjusting throttle valve 38. Throttle valve 21 setsthe pressure P at port 20 and the pressure P, at port 19 is determinedby the feed pump 17. The pressure at the input of slurry pump 33 issomewhat lower than the pressure at the top of the column due to thepressure drop from the losses between the entrance port 19, and theentrance to the slurry pump 32.

The system of throttle valves and pumps shown in FIG. 5 is used forillustration only. Various other types of controls may be used toachieve the pressure distribution (shown in FIG. 5A) which is necessaryfor correct operation of the column.

The embodiment discussed above with reference to FIG. 5 shows a systemwhich utilizes a single resin driver zone shown as zone 13 at the lowerend of the column. In some cases, however, depending upon the geometryof the column, the fractional forces present between the porous bed andthe inner surface of the column may be high enough that the use of sucha single driver zone may not be adequate to overcome such forces so asto maintain the upward motion of the bed without an excessive stress onthe resin beads. This effect is particularly noticeable for relativelylong columns inasmuch as such forces build up rapidly as a function ofthe length of the column, as discussed generally by H. L. Brandt and B.M. Johnson in the article Forces in a Moving Bed of Particulate SolidsWith Interstitial Fluid Flow, in Al. Ch. B. Journal, vol. 9, No. 6November 1963, p. 771. In such instances it may be desirable to utilizeone or more additional driver zones inserted at appropriate locationsalong the column.

Such a structure is shown in FIG. 6, for example, in which correspondingreference numerals identify elements corresponding to those of FIG. 5and in which an additional auxiliary driver zone 45 is positionedbetween the primary reaction zone 11 and the wash and separation zone41. As shown, a drive pump 46 is used to pump a portion of the treatedliquid which exits from port 20 back into the column at port 47. Thus, afirst portion of the treated liquid entering port 47 is used to forcethe porous bed upwardly through driven zone 45.

In this structure all of the liquid flowing upwardly in auxiliary driverzone 45 and all of the liquid flowing downwardly in primary reactionzone 11 exit together from the column at port 20. Unlike the isolationoperation discussed previously with reference to separation zones 41 and42, no isolation, or separation, zone is formed between primary reactionzone 11 and auxiliary driven zone 45. Instead, the operation at port 20is similar to that described in the above reference Probstein andShwartz patent application wherein both liquids are permitted tointeract, or mix, completely in their simultaneous exit from port 28.Although an effective liquid displacement action occurs so as to form acrown 48 near port 20 where both liquids exit, there is no need tocontrol the amount of mixing thereof since, at such point, both liquidsare the same (i.e., treated liquids). Hence, a complete mixing of themcan be permitted and the need for the formation of an isolation zone inaccordance with the invention is avoided. The operation at port 20,therefore, can be contrasted with the operation of separation zones 41and 42 where, as discussed previously, only a small, and controlled,amount of one liquid is permitted to mix with another different liquidand a complete mixing, or interaction, between the two different liquidsis prevented.

A second smaller portion of the liquid entering port 47 is forceddownward into the wash and separation zone 41, the latter zone isolatingthe auxiliary driver zone 45 from regeneration zone 12 essentially inthe same manner as discussed previously with reference to FIG. 5.Further, a throttle valve 49 has been added at the output of port 36 toallow the pressure P at port 36 to be greater than the base atmosphericpressure.

FIG. 6A shows the pressure distribution along the column for theconfiguration of FIG. 6. In this particular embodiment the baseatmospheric pressure P is at port 20 at which port the output treatedfluid product exits. The pressure at port 47 is identified as P and iswell above the pressure P at port 20 and also above the pressure P atport 37. The relationship among the pressures P P P P and P issubstantially the same as that shown in FIG. 5A, all of such pressuresin efiect having been pressure biased upwardly as a result of theinsertion of driver zone 45.

Other insertions of additional driver zones at other alternativelocations along the column may be required in any particular applicationof the invention and can be readily worked out for specifically desiredoperating conditions in accordance with the principles of the invention.

As one particular example of the possible dimensions and pressuresinvolved in a column of the invention, the following exemplary valuesare given, such values being related, for example, to the embodimentshown in and discussed with reference to FIGS. 6 and 6A above.

DIMENSIONS Total column length feet 10.5 Column diameter (at primaryreaction zone 11) inch 8 Column diameter (at regeneration zone 12) do 4Length of primary reaction zone 11 feet 2 Length of driver zone 45 do 2Length of Washing zone 14 do 1 Length of separation zone 41 do 1 Lengthof regeneration zone 12 do 2 Length of separation zone 42 do 1 Length ofresin driver zone 13 do 1.5

PRESSURES P =Between 9 to 9.5 atmospheres P =ApproX. 9 atmospheres(below P but above P P '=Approx. 9 atmospheres (below P P =Approx. 9atmosphers (above P and P P '=Approx. 9 atmospheres (below P and P P'=Approx. 9 atmospheres (above P but below P P =1 atmosphere 1 :3atmospheres For a column of such size and pressure relationships, therate of removal of treated liquid product will be approximately 60,000gallons per day. Such a figure can be compared with the maximum outputof about 800 gallons per day for comparably sized continuously operatingcolumns of the prior art described above. In general, for product outputrates lower than above mentioned design values for the system forcarrying out the process of the invention, all pressure differences usedin the columns will be scaled down approximately proportionately to thereduction in product rate.

In a single vertical column of the types described with reference toFIGS. 5 and 6, for example, the regeneration zone 12 and the resindriver zone 13 at the bottom of the column are eiiectively isolated asdiscussed above in the vicinity of port 36 by the crown 40 formed asshown and the regeneration zone 12 is effectively isolated from eitherthe primary reaction zone 11 or the auxiliary drive zone 45 in thevicinity of port 37 by crown 39. The formation of such isolation crownswill occur without instabilities if the density of the uppermost liquidis substantially the same as, or less than, that of the lowermost liquidat the crown in question. Such isolation can still prevail even if theuppermost liquid has a slightly higher density than that of thelowermost liquid provided the fluid allow rates through the resin bedare high enough to prevent instabilities which lead to the passage ofthe heavier fluid into the lighter one via finger-shaped regions(fingering instability), a phenomenon generally discussed, for example,in the article, Mechanisms Affecting Dispersion and MiscibleDisplacement, by Richard I. Nunge and William N. Gill, published in FlowThrough Porous Media, pp. 179-196, American Chemical Society,Washington, DC, 1970.

However, if the density of the uppermost liquid is higher than that ofthe lowermost liquid and the fluid flow rates are insufiicient, anunstable condition will occur and the heavier liquid will tend to movedownwardly through the crown in question and efiFective stabilizationcannot be maintained for purposes of isolation as desired.

For example, if the regenerant liquid is heavier than the liquid undertreatment, an instability can occur at crown 40 where the regenerantliquid will tend to move down- 'wardly through crown 40 toward thebottom of the column. In such case no instability occurs at crown 39since the heavier regenerant liquid is below the crown and the lightertreated liquid is above the crown. In such a case, an alternativeembodiment of the invention, as shown in FIG. 7, may be used-to overcomethe possibility that such instability may occur.

As can be seen in FIG. 7, the portion 50 of the column, effectivelyrepresenting the regeneration zone 12 is formed in a U-shapedconfiguration, the structure and reference numerais relating to theremainder of the column corresponding to those shown in FIG. 5. In suchconfiguration, the heavier regenerant liquid is then effectively placedbelow the lighter untreated liquid in the driver zone at a position nearport 36, which, as shown, therein, is at the righthand end of U-shapedportion 50. Accordingly, while the overall operation of the coumnremains essentially the same as before, the potential instability isremoved and, as before, the crown 40 is formed at port 36 so thatisolation occurs between the resin driver zone 13 and the regenerationzone 12. The untreated liquid in driver zone 13 is moving downwardly inthe column at the right and is thereby prevented from entering theregeneration zone while the regenerant liquid which is moving upwardlyin the column at the right is prevented from passing into the resindriver zone. In all other respects the overall operation of the columnis substantially the same as that shown and described with reference toFIG. 5.

Alternatively, if the liquid under treatment in the embodiment of FIG.5, for example, is heavier than the regenerant liquid, an instabilitycan occur at crown 39, and the entire system shown in FIG. 7 may beinverted so that the curved section 50 has the highest elevation. Theheavier treated liquid is then below crowns 39 and 40 formed at port 37and 36 respectively, and the lighter regenerant liquid is above, asrequired for stability.

In the embodiments shown and discussed above, which represent exemplaryembodiments of the invention, the advantages of the system for carryingout the process of the invention are readily apparent when the operationand structure thereof are compared to presently available fiuid solidcontact processing systems. Insofar as the inventors presently know,this invention represents the only etfective, truly continuousfluid-solid contact process that can achieve high output product rateswith stable operation. In contrast with semi-continuous systems, nointermittent operation of any portion of the system is required.Moreover, the steps of the process of the inven tion are adapted topermit the effective embodiment of the systems in a single column,wherein a packed porous bed of solid material is continuously movedthrough the various operating zones of the column and eiiectiveisolation of such zones is achieved, where necessary, by using stablyoperated fluid displacement techniques. The rate of rise of the porousbed can be controlled in a substantially independent fashion (i.e., suchrate of rise is not dependent to any great degree upon any othercharacteristics of the system, once the pressures P P P P P (ifpresent), and P are selected for a desired operating condition) bymaintaining an appropriate overall pressure difference (P -P across thecolumn and controlling the scraping rate at the top of the column. Thecapability of using a single column in a preferred embodiment of theinvention to perform all of the operating steps involved avoids the needfor a plurality of valves, or other mechanical devices for controllingthe passage of solid material or other material from one column toanother as is required in a multi-column structure. Thus, the physicalcharacteristics of the solid material are not subject to any substantialalteration because of the use of such mechanical devices. The onlyregions of the system for carrying out the process of the invention inwhich the solid material is subjected to mechanical perturbations in theembodiments discussed above are at the slurry pump and at the scrapermeans.

However, the invention is also adaptable to multiple column operationwhich may be desirable in some applications, particularly where mixedbed operation is to be achieved.

Since the operation of the system of the invention is truly continuous,there is no need to program the operation of any of the steps in theoverall process in an intermittent fashion, as in the Asahi or Higginssystems, or other nearly continuous systems, presently known in theprior art. Thus, once the system has been set into operation, no furthercontrol or programming is required other than for the provision of aconvenient method for monitoring various operating characteristics ofthe system to determine whether the desired operation is being achieved.In some applications, as mentioned previously it may be desirable toprogram the operation of the invention even though a programmedoperation is not necessary to the basic principles of the operationthereof. In such instances, for example, the amount of treated liquidremoved from the system (i.e., the production rate) may be varied, ifdesired, by programming the pressure relationships set up for operationto produce the variations required.

In operation of the system for carrying out the process of theinvention, the primary reaction zone 11 and the regeneration zone 12remain in substantially the same locations within the column and needonly be of suflicient length to provide for an eflicient ion exchangeoperation. Thus, in the primary reaction zone 11 ion exchange resin isdepleted to a predetermined value when it reaches the top of the zoneand the untreated liquid is processed by the time it reaches port 20.

Further, in the regeneration zone 12 the depleted resin is regeneratedby the time it reaches the separation zone 41 and the regenerant liquidis depleted when it reaches port 36. Thus, the overall resin inventoryis reduced considerably from that required in prior art systems. In thepreferred embodiments of the invention described above only a singletransfer line, i.e., the slurry line 29, for example, is required forconveying solid particles, as contrasted with the multitude of transferlines for the resin material that are used in the multi-column systemsof the prior art.

The overall operation, therefore, provides great improvement in ionexchange efliciency both in the primary reaction zone and in theregeneration zone and considerably reduced costs of initial installationand subsequent operation.

Although the above embodiments have been described, for clarity, asutilizing a single column construction, the principles of the inventionutilizing the continuous operation of the ion exchange and driver zonestherein as well as the washing and separation zones therein can in someapplications be embodied in more than one columnar entity, if desired,with appropriate means for feeding materials from one zone to anotherbetween columns. Further, though the above discussion, again forclarity, is shown with reference to vertically oriented structures, itis clear that the apparatus may be horizontally oriented, or orientedsomewhere in-between, for some applications. The system is not dependenton gravity force components for its operation and, accordingly, itsorientation can be set entirely independent thereof.

What is claimed is:

1. A process for isolating the flow of a first fluid flowing at a firstrate in a first zone of a column from the flow of a second fluid flowingat a second rate in a second zone of said column in which column apacked porous bed of solid material is moving through said zones at athird rate, said process comprising the steps of:

permitting a controlled portion comprising at least a part of said firstfluid to flow from said first zone toward said second zone at a fourthrate;

permitting a controlled portion comprising at least a part of saidsecond fluid to flow toward said first zone at a fifth rate;

independently controlling said fourth and said fifth flow rates so as topermit the removal of said controlled portions of said first and secondfluids simultaneously at a position intermediate said first and secondzones, thereby forming an isolation Zone between said first and saidsecond zones to prevent any of said first fluid from 14 entering saidsecond zone and any of said second fluid from entering said first zone,and removing said controlled portions of said first and second fluidsfrom said column at a position in said isolation zone.

2. A process in accordance with claim 1 wherein said controlled portionof said first fluid comprises all of said first fluid.

3. A process in accordance with claim 1 wherein said first fluid flowsin said first zone in a direction opposite to the flow of said secondfluid in said second zone.

4. A process in accordance with claim 1 wherein said first fluid flowsin said first zone in the same direction as the flow of said secondfluid in said second zone.

5. A continuous fluid-solid contact process comprising the steps ofcontinuously supplying a first fluid material to a fluidsolid reactionzone;

continuously removing reacted portions of said first fluid material fromsaid reaction zone;

continuously supplying a second fluid material to a second zone;

continuously forming a porous bed of solid material and moving saidporous bed through said reaction zone and through said second zone incontact with said first and second fluid materials;

continuously permitting controlled portions of said first and saidsecond fluid materials to flow in a first isolation zone intermediatesaid reaction zone and said second zone;

continuously removing said controlled portions of said reacted portionsof said first fluid material and of said second fluid material from saidfirst isolation zone; thereby forming an isolation crown in said firstisolation zone to prevent said first fluid material from entering saidsecond zone and said second fluid material from entering said reactionzone, and continuously removing the remainder of said second fluid at apoint remote from said first isolation zone.

6. A continuous fluid-solid contact process in accordance with claim 5wherein said first fluid material is an untreated fluid material,

said reacted portions are treated fluid material, and said fluid-solidreaction zone is a primary reaction zone;

wherein said second fluid material is a regenerant fluid material andsaid second zone is a regeneration zone; and further wherein said porousbed of solid material continuously moves through said regeneration zone,said first isolation zone, and said primary reaction zone in contactwith said regenerant fluid material and in contact with said untreatedfluid material.

7. A process in accordance with claim 6 wherein said porous bed isformed in a driver zone and further including the steps of continuouslyforming a slurry comprising said solid material of said porous bedleaving said primary reaction zone and said untreated fluid material;continuously moving said slurry to said driver zone; continuouslyremoving a part of said untreated fluid material from said driver zone;permitting a controlled portion of said regenerant fluid and acontrolled portion of said untreated fluid to flow in a second isolationzone intermediate said regeneration zone and said driver zone; and

continuously removing said controlled portions of said regenerationfluid and said untreated fluid from said second isolation zone;

thereby forming an isolation crown in said second isolation zone toprevent said regenerant fluid from entering said driver zone and saiduntreated fluid from entering said regeneration zone.

8. A process in accordance with claim 7 and further including the stepof adding said part of said untreated 15 fluid material being removedfrom said driver zone to a supply of untreated fluid material, at leasta part of which is beingsupplied to said primary reaction zone.

9. A process in accordance with claim 7 and further including the stepof controlling the rate of movement of said porous bed by controllingthe pressure difierence (P -P wherein P represents the pressure at whichsaid slurry enters said driver zone and P represents the pressure, lessthan the pressure P at which said untreated fluid material is suppliedto said primary reaction zone, whereby the rate of movement of saidporous bed through said driver zone, said regeneration zone, saidprimary reaction zone and said first and second isolation zones iscontrolled.

10. A process in accordance with claim 9 and further including the stepof independently controlling the pressure at which said part of saiduntreated fluid is being removed from said driver zone at a pressure Pwhich is below said pressure P 11. A process in accordance with claim 10and further including the step of independently controlling the pressureat which said controlled portions of said regenerant fluid and saiduntreated fluid are being removed from said second isolation zone at apressure P which is below said pressure P 12. A process in accordancewith claim 11 wherein said pressure P is maintained at atmosphericpressure.

13 A process in accordance with claim 11 and further including the stepof independently controlling the pressure at which said regenerant fluidmaterial is being supplied to said regeneration zone at a pressure R;which is above said pressure P 14. A process in accordance with claim 13and further including the step of independently controlling the presl 6sure at which said reacted portion of said untreated fluid material isbeing removed from said primary reaction zone at a pressure P which isbelow said pressure P7.

15. A process in accordance with claim 14 and further including the stepof independently controlling the pressure at which said controlledportions are being removed from said first isolation zone at a pressureP which is below said pressure P 16. A process in accordance with claim15 and further including the step of continuously moving said porous bedthrough an auxiliary driver zone positioned intermediate saidregeneration zone and said primary reaction zone.

17. A process in accordance with claim 16 wherein a portion of saidtreated fluid material being removed from said primary reaction zone issupplied to said auxiliary driver zone at a pressure P which is abovesaid pressure P References Cited UNITED STATES PATENTS 6/1972 Minart210-33 OTHER REFERENCES SAMIH N ZAHARNA, Primary Examiner R. A.S-PITZER, Assistant Examiner U.S. Cl. X.R.

3 UNITED STATES PATENT OFFICE CEETH ICATE ()F CORRECTION Patent No.751,362 Dated August 7, 1973 I Ain A. Sonin, Ronald F. Probstein, andJosef Shwartz It is certified that error appears in'the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

' Column 2, line 72, for "critically" read--criticality--; Column 5,line 61, for "115" (second occurrence) read--ll6--; Column 5, line 64,

for "115" read--ll6-; Column 8, line 22, for "pumped" read--dumped--;Column 9, line 64, for "32" read--33--; Column 9, line 75, forfraction'eml read--rictional-; Column 10, line 24, for "driven"read--driver-; Column 10, line 31, for "driven" read--driver--;

Column 10, line 36, for "28" read--20--; and Column 12, line 10,

for "coumn" read--column--.

Signed and sealed this 18th day er December 1973.

(SEAL) Attest:

EDWARD M. FLETCHER, JR. RENE D. TEGTMEYER Attesting Officer- ActingCommissioner of Patents

